I recently asked for help on the left channel of the PWD breaking up, and consequently the sound became untenable. However that post seems to have been lost but because i raised the issue i thought i had better close it.
Since then i took it to the local distributor and over the ensuing weeks of backwards and forwards, changing boards in and out we finally got to the bottom of it being a dodgy analogue output board.
Its been back in my system for a couple of days now and touch wood it sounds great and strangely also a lot more reliable in playing nice.
Thank you.
Congratulations on your repaired PWD and thanks for the info. NOW! Enjoy your now fully functional PWD. 
J.P.